The present invention relates to naptha-soluble, hydrogenated alkyl aryl ketone/formaldehyde resins, as well as to the manufacture thereof.
Alkyl aryl ketone/formaldehyde resins have been known industrially for a very long time. The disadvantages inherent in these resins can, in part, be compensated for by a hydrogenating treatment.
Such a process is described in German Pat. No. 870,022. This reference teaches that the starting resins can be hydrogenated to varying extents, depending on the selection of the reaction conditions. The resins showed marked differences in their properties depending upon the degree of hydrogenation, as measured by the oxygen content still present in the resultant products.
With a drop in oxygen content, a reduction of the softening point was also observed--down to a softening point of about 50.degree. C. with an oxygen content of about 4% by weight (starting resin: acetophenone/formaldehyde resin--softening point: 68.degree. C., oxygen content: about 13% by weight). An advantage of the prior art hydrogenated resins with a low oxygen content was their excellent solubility in naphtha, which is very frequently utilized as a solvent in the paint industry. The starting resins and also their hydrogenation products of a higher oxygen content were, however, practically insoluble in aliphatic hydrocarbons.
Although such hydrogenated resins were very readily soluble in naphtha, a marked disadvantage was their low softening point, which rendered them poorly suitable for practical applications.
Thus, the prior art teaches that progressive hydrogenation, and concomitant lowered oxygen content, of the starting resins, increases their naphtha solubility to the desired extent, but simultaneously lowers their softening point to such a degree that the resultant hydrogenated resins are in many cases unsuitable for commercial applications.